Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

738
FXUS63 KLOT 071812
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
112 PM CDT Thu May 7 2026

.KEY MESSAGES...

- Occasional chances for scattered rain showers will continue
  into next week.

- Temperatures will gradually warm through Saturday before
  trending cooler early next week.

&&

.DISCUSSION...
Issued at 111 PM CDT Thu May 7 2026

Expansive upper-level cyclonic flow remains entrenched across
the Upper Mississippi River Valley, which is leading to a
continuation of the generally cool and, at times, showery
pattern. An upper-level shortwave propagating around the outer
periphery of the cyclonic flow continues to pivot southeastward
across the area this afternoon, which with steep lapse rates
(500mb temperatures sampled near -28C on the 18Z DVN RAOB), is
supporting widely scattered showers at press time. The highest
coverage of showers through the afternoon and evening should
generally favored near and south of I-80 (near a remnant
boundary) and near the Wisconsin state line (near the core of
the coldest mid-level temperatures). Southwest winds will
remain gusty (30 to locally 40 mph) this afternoon, especially
near showers where the deep layer of dry sub-cloud air will lead
to efficient downward momentum transfer.

Tonight, coverage of showers should tend to favor areas south
of Interstate 80 as additional subtle DCVA rides atop the
aforementioned frontal boundary. A gradient in cloud cover will
set the stage for a gradient in overnight lows, with values
expected to fall toward the mid to upper 30s near the Wisconsin
state line to the upper 40s near US-24. Patchy frost formation
will be favored north of Interstate 88 and especially near the
Wisconsin state line, though will withhold a Frost Advisory
given the expectation for upper-level clouds to thicken toward
daybreak (which may stall the downward dive in temperatures).

Tomorrow, another upper-level shortwave will pinwheel through
the upper-level cyclonic flow and support the development of
showers and perhaps a thunderstorm along the stalled frontal
boundary. Forecast guidance continues to exhibit spread in the
location of the boundary by tomorrow afternoon, though have
noted a slight southward trend in the latest guidance. As a
result, will paint low-end chance (20-40%) PoPs south of I-80
tomorrow, with the highest values near US-24. Elsewhere, partly
cloudy skies and a modest push of low-level warm-air advection
will help boost highs into the mid to upper 60s. Yet another
upper-level shortwave will move across the region on Saturday,
presenting another opportunity for a few showers. Temperatures
on Saturday look to be the warmest of the past few days with
highs in the upper 60s (north) to mid 70s (south).

Another reinforcing shot of seasonably cool air will follow the
front Saturday night and result in a swift return to somewhat
below average temperatures Sunday into the beginning of next
week. With that said, ensemble guidance continues to advertise a
strong signal for a notable warming trend by the May 16 to 17
timeframe, which is in line with climatology.

Borchardt / Izzi

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1222 PM CDT Thu May 7 2026

Southwesterly winds will become increasingly gusty through
early this afternoon at the terminals, and the potential exists
for a brief period of gusts near 30 kts through mid afternoon.
Otherwise, an area of showers will generally track near/south of
I-80, and have added a VCSH mention at GYY to account for this.
At the Chicago-area terminals, the chances for precip directly
impacting the terminals remains about 20-30 percent, too low to
warrant a transition to VCSH and/or TEMPO groups.

One item we are closely monitoring is the potential for a lake
breeze (possibly augmented by gusty outflow) to push southward
towards primarily ORD later this afternoon and early evening.
Chances remain too low to introduce a specific mention in the
TAFs, but monitoring the 21-00z timeframe in particular for
this with the boundary becoming apparent near the Lake County
shoreline. If scattered convection develops near the WI state
line, this may further increase the potential for a NE wind
shift at ORD.

Otherwise, VFR will prevail tonight into Friday. Light and
variable winds should trend light southwesterly through Friday
morning. Lots of variability in the wind forecast for Friday
afternoon, ranging from a lake breeze passage at the Chicago
terminals to increasing SW breezes. Have continued to prevail
light SW winds in the latest TAFs, but alterations may become
necessary in future updates.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 6 PM CDT this evening for Wilmette
     Harbor IL to Burns Harbor IN.

&&

$$

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